If you still want to sneak around, I'd go illusion. Quiet casting magic on a sneaky type character is invaluable. Conjuration ALWAYS gives away your position, even with quiet casting as NPC's will detect your summon and never seem to have trouble figuring out where it comes from... at least for me. And besides, sneaking in the middle of a large group and casting mayhem seems a lot more fun to me anyway.

Dammit now I'm unsure again... :'(

This is why RPG's kick my ass.

This is how Conjuration works:

1. /summon Storm Atronach

2. /grab popcorn and watch your enemies get [censored] in the face

Fair enough, good option too.

Having a look at your build plan, my opinion:

• Why are you going up to daedric smithing? I wouldn't bother with smithing perks at all to be honest, you can find strong daggers you can enchant, or buy them from tonilia. Remember they do 2x damage when power attacking, and 15x sneak damage with the perk, 30x if you use the DB gloves. You really don't need to be able to improve them to that extent, you can do enough damage without it on master, trust me. Possibly think of steel and arcane smithing perks, you can then improve any dagger you find, the unique daggers have some useful enchantments, e.g. insta kill.
  
• Most of the alchemy perks, really aren't worth it IMO, poison resistance? I have never needed that, even against chaurus. I don't think you need the last perk either, you control what potions/poisons you make so you can have what you want, plenty of ingredients. I would only go up to the concentrated poison perk and the benefactor perk, all the others are novelty to be honest.
  
• Sneak perks, you don't really need to take the first perk 5x, all it adds is +5% for the last 4 perks. You can sneak perfectly fine without them.
  
• Enchanting, the elemental enchantments aren't that useful, the damage isn't multiplied by sneak hits. You are better of going up the middle tree and using 1 second paralyse enchantments or 1 second fiery soul trap enchantment (soul trap and 10 fire damage, gives you a good 600+ charges). 1 second paralyse is brilliant for dual wield daggers, due to the speed.
  
• One handed perks, maybe think of using the fighting stance and savage strike perks, power attacks are very strong when dual wielding.
  
• Consider illusion, fits very well for your character. You can use the basic fury/calm/fear spells at any levels with the right perks. Then you can consider playing as a vampire, you get a sneak and illusion bonus. You also get 100% poison and disease immunity, so you won't need the alchemy perk mentioned above.
  
• If you plan to go that far with the pickpocket perks, you might as well get the +100 carry capacity perk, so you can carry around more loot.

Thank you, finally someone who breaks down my skills and tells me what to do

My only reason for not choosing Illusion is this. I can pretty much just make every illusion spell with Alchemy right?

I'm a big Alchemy fan. That's why I chose almost all the perks. Though, I suppose Purity and Snakeblood are useless, especially considering I am becoming a Vampire, which would also boost my Illusion.

Necromancy probably wouldn't suit me very well as my enjoyment comes from the difficulty of taking out every single opponent without detection. But the choice is definitely between that and Illusion.
I also have no idea what perks I should take for Illusion...

Okay, given that information. Break it down and give me orders, oh kind Bobjim

The elemental perks are mainly for mages who have 100% cost reduction so that even maxed out enchants have infinite uses. Depends on your build.

Absolutely not, I thought this at first, but the effects such as fear you get from poisons are to weak for use. Illusion spells work because you can dual cast them, so you get x2.2 effectiveness.

If your becoming a vampire, defo go with illusion, it gets a nice buff. It's more suited to your playstyle than conjuration. This is really similar to my playstyle ha

Well you could use necromancy, just go down the middle path for conjuration, only requires 4 perks. You get double duration for reanimated undead, they are pretty strong as well for the early levels. You can then use dead thralls, which are pretty awesome. The problem is magicka cost, which is huge.

But really, just play and experience it. I don't really plan my build much, just improvise as I go along.

Ah, the elemental enchantments benefit from fortify destruction?! Didn't know that, I usually ignore them, even though my character uses destruction. Might have to start using them.

One last thing. If you do this well enough I'll know for sure

Can you give me some examples of when/how I would use Illusion to help me sneak through a dungeon or robbing a house?

You might be interested in this thread:
http://www.gamesas.com/topic/1312501-the-way-of-the-artificer/page__fromsearch__1

Two enemies up ahead, you sneak kill one, the other notices. You then calm the other one, then resneak and sneak kill him, boo ya. It also helps when you are under attack by a few enemies you couldn't sneak from, so before you whip out your dual daggers you fury the strongest one for an easier battle. Less heat.

Robbing a house, if you get caught, using calm on the person so they don't mind, they won't then call the guards.

Thanks for that, I had no idea of the link between the two.

Thank you. Honestly, I'm glad you popped in my thread. Also thank you to Penderghast who tried to tell me the exact same thing.

About my perks. Taking what you said into consideration I removed some alchemy perks and added some one handed and got this: http://skyrimcalculator.com/#44009

I haven't added anything into Illusion because I honestly don't know which ones will be helpful to me.

If you just want to try out raising dead bodies, go get the Ritual Stone power. It will allow you to do basiclly the raise dead thing once a day.

A little late I know, but imo conjuration doesn't work as well as I thought it would with the playstyle. Casting a great honking light when I'm trying to be stealthy just felt weird. I tried it for a few levels when I first bought the game and ended up just scrapping the character entirely.

It's not that the summon isn't useful, it's that it felt like it was defeating the purpose of my playstyle.

http://skyrimcalculator.com/#44021

Could I suggest that ^. I have taken the damage perks down to only 1 for 1h and archery, I don't usually need that extra power. Considering you get a big sneak crit bonus. You need all the illusion perks to be honest, not right away though, dual casting and the right tree will do for the first ~30 levels.

I reduced the first sneak perk as well, honestly it's not needed. Especially with the +25% you get for being a vampire.

This is a good point, it's an area effect power as well, so you can raise a few dead bodies. Even mammoths ha.

Also you get a vampire power that allows you to raise undead.

That only adds up to 65, so I could add the damage for Archery and 1h back right? Sometimes I can't sneak and get those multipliers, like dragons for example.

Yeah sure, go for whatever you want to be honest

Dragons aren't usually a problem if you have a ranged weapon I find, it's not to difficult to avoid their attacks and keep hitting them with archery. Another thing I just thought of, illusion gives you the invisibility and muffle spells, a godsend to sneak players. Combine the two and you will be a sneak god. When you get the last sneak perk, you can hide from anything, anywhere.

Edit: Like the person below states, you probably won't go to level 81. The highest I have went is level 68 IIRC, maxed out all the skills I used. With this build you will probably go to level 60, so most of your perks should be okay. I wouldn't do that plan exactly, just improvise and have an idea in your mind.

I wouldn't suggest planning your character out to 81 if that is what you are doing. You will max out the skill and not have the perks to fill it in.

Most character builds are going to be maxing out around lv 30-40.